Water purification system and method

ABSTRACT

The invention concerns a water purification system ( 100 ) comprising a closed water recirculation loop ( 106 ) supplied at one point by a water inlet ( 101 ) with water to be purified, (and having) at least one outlet point of use of the purified water ( 102 ) and (further comprising) pumping means ( 103 ) and water purification means ( 150 ) on the loop respectively downstream of the inlet point and upstream of the at least one outlet point ( 102 ), in the water flow direction which system is characterized in that it includes two independent valves: 
         a first valve ( 130 ) on the loop upstream of the pumping means ( 103 ), and    a second valve ( 120 ) upstream of the at least one point of use outlet point ( 102 ). The invention also relates to a water purification method.

The present invention consists in a water purification system. Moreprecisely, the present invention consists in a water purification systemof the type equipped with a purified water recirculation loop. Thepresent invention also relates to a water purification method using thissystem.

Many applications require the use of ultrapure water, in particular inbiological and chemical analysis laboratories. Water purificationsystems have been designed for this purpose.

Depending on the volumes of water that these applications require, thepurification systems are required to distribute purified water at theirmaximum treatment throughput, at a throughput very much less than theirmaximum treatment capacities, or even sometimes at a nil throughput.Moreover, in some cases, it is necessary to deliver a predeterminedvolume of purified water, and it is therefore beneficial to be able toautomate the distribution of a given volume without the user beingobliged to monitor the filling of the given volume. These variations ofthroughput in this kind of system cause a number of problems, inparticular water stagnation problems, which compromise its purity.

The problem is therefore to design a water purification system adapted,as required:

-   -   to distribute purified water at a maximum treatment throughput,        for example to fill a container as quickly as possible,    -   to distribute purified water at a very low throughput, for        example to adjust the water level in a container, and    -   to distribute purified water automatically (volumetric mode) by        programming a certain volume of water to be delivered, for        example to fill a container, at the same time as providing the        best possible water quality regardless of the selected mode of        operation and at any time, in particular when water has not been        drawn off for some time.

Several solutions to this technical problem have been proposed. Theygenerally provide water purification systems comprising a waterrecirculation loop fed at one point by an inlet for water to be purifiedand having at least one purified water point of use outlet, and pumpingmeans and water purification means disposed in the loop respectivelydownstream (relative to the water circulation direction) of the inletpoint and upstream of the at least one outlet point. The recirculationloop design is an effective way to circulate water permanently in thesystem, avoiding problems linked to stagnation of the water, andenabling the user to obtain purified water at the point of use at anytime.

A first prior art type of system of this kind includes a three-wayoutlet valve that is manually operated to divert water to the outletpoint and/or to the recirculation loop. Accordingly, the user candistribute purified water to the point of use either at a highthroughput or at a low throughput at the same time as maintaining aconstant flow through the water purification means.

This type of valve being manual, it cannot provide an automaticdistribution mode for filling a predetermined volume.

Another type of prior art water purification system includes at theoutlet a three-way solenoid valve of the on/off type with a normallyclosed (NC) flow path and a normally open (NO) flow path.

This solenoid valve enables the user to deliver a predetermined volumeautomatically, although without the possibility of adjusting thedistribution throughput.

One solution would entail operation in volumetric mode using anelectromagnetically controlled proportional three-way valve. However,this type of valve is costly, bulky and complex. In this case, thevolumetric distribution mode imposes a very fast change from therecirculation position to the distribution position of the valve, theresponse time and the inertia of the valve conditioning the accuracy ofthe volume delivered.

Moreover, all three-way valves rule out the simultaneous use of two (ormore) points of use.

A third type of prior art system includes a distribution pump, a manualtwo-way valve or a two-way solenoid valve and a spring-loaded checkvalve in the recirculation loop. This enables the user to distributepurified water at a selected throughput at the same time as maintaininga constant flow in the filter means, unused water being recirculated viathe check valve. In this system, in the case of an on/off type solenoidvalve solution, the user can distribute a predetermined volumeautomatically (volumetric mode). In the case of a distribution pumpequipped with a variable speed motor, distribution with any throughputis possible but leads to a variation of the flow in the water treatmentmeans. This latter solution therefore caters for a volumetric mode ofoperation as referred to above. In systems of this type the points ofuse are equipped with a filter.

The above type of system is described in particular in the documentWO98/052874.

The problem with this type of system equipped with a two-way valve and apreloaded check valve is that the head loss induced in the filter at thepoint of use at the maximum treatment throughput of the treatment meansmay cause the check valve to open and allow some of the water in therecirculation loop to pass through it, degrading the performance of thesystem and the volumetric distribution function. Moreover, in this typeof system, in recirculation mode, the purified water is recirculated atthe calibration pressure of the check valve, which means that thetreatment means remain pressurized and a throughput peak occurs when thedistribution valve opens.

The invention aims to alleviate these disadvantages.

A first aspect of the invention proposes a water purification systemcomprising a closed water recirculation loop supplied at one point by awater inlet with water to be purified and having at least one outletpoint of use of the purified water and further comprising pumping meansand water purification means on the loop respectively downstream of theinlet point and upstream of the at least one outlet point, in the waterflow direction, which system is characterized in that it includes twoindependent valves:

-   -   a first valve on the loop upstream of the pumping means, and    -   a second valve upstream of the at least one point of use outlet        point.

Thus the present invention proposes to use two two-way valves, with oneof them in the recirculation loop, with no additional back-pressuredevice (for example a preloaded check valve), and the other on thedownstream side of the outlet from the treatment means, and used todistribute purified water.

According to preferred features of the invention, which may whereapplicable be combined:

-   -   the two valves are solenoid valves of the type with two normally        closed (NC) flow paths;    -   the system further comprises a control unit for the valves that        includes a user interface;    -   the valve control unit further comprises a memory for saving        data supplied by a user;    -   the water purification system comprises a hydraulic connector        forming a distributor or manifold for a hydraulic circuit        including a purified fluid inlet and three outlets, the inlet of        the connector is connected directly to the first outlet by a        pipe and a second pipe is connected hydraulically to the first        pipe between said inlet and said first outlet and to a third        pipe having two ends forming the other two outlets of the        system;    -   the water purification system comprises two parallel branches        that come together downstream of the hydraulic connector;    -   the two parallel branches are made from thermoplastic materials        such as polyethylene, polypropylene or polytetrafluoroethylene.

The invention also relates to a method of using a system of the abovekind that comprises the steps of opening the first valve, calledrecirculation valve, and closing the second valve, called distributionvalve, to recirculate all the water treated by the treatment means.

According to preferred features of the invention, which may whereapplicable be combined, the method further comprises:

-   -   the steps of opening the first or recirculation valve and        opening the second valve, called distribution valve to        distribute purified water at a low throughput;    -   the steps of closing the first or recirculation valve and        opening the second valve, called distribution valve to        distribute purified water at a high throughput;    -   a step of capturing a value for the volume of purified water to        be delivered entered by the user on the user interface, a step        of storing that value in the memory of the control unit and a        step of automatically distributing the entered volume of water,        a fast change from a recirculation mode to a distribution mode        being obtained by instantaneously opening the distribution valve        and closing the recirculation valve.

It is preferable if two two-way on/off type normally closed (NC)solenoid valves are used, as this caters for four state combinations:Open-Open, Open-Closed, Closed-Open, Closed-Closed, each correspondingto a different mode of operation of the system.

This technical solution meets all the requirements for a waterpurification system mentioned above at the same time as proposing adesign that is economic, easy to use and easy to maintain. Inparticular, it offers operation in the three modes described above.

In the recirculation mode, in which the recirculation valve is open andthe distribution valve is closed, water is not distributed by thesystem, the outlet valve being closed. Consequently, all water leavingthe treatment means is recirculated to the treatment means via therecirculation valve.

In the low throughput distribution mode (throughput equivalent or closeto a dropwise rate), both valves are open to distribute purified waterat a low throughput and to recirculate the remainder in therecirculation loop. The proportion of the water produced that isdistributed is a function of the design and the sections of thedistribution and recirculation pipes.

In the high throughput distribution mode (throughput equal to thenominal throughput given by the distribution pump), the recirculationvalve is closed and the distribution valve is open. Recirculation is nolonger possible and all treated water is distributed via thedistribution valve.

Finally, the fourth combination of the states of the two valves, withboth valves closed simultaneously, yields a fourth mode of operation,namely an idle position mode with the distribution pump stopped and thewater treatment unit completely isolated from the points of use.

This mode is used for system maintenance, for example replacingcomponents of the water treatment means.

According to a preferred feature of the invention, which may whereapplicable be combined with others, the solenoid valve control systemmay have a volumetric automatic mode for distributing a precise presetquantity of water that successively combines the recirculation mode andthen the high throughput mode. In this volumetric mode of operation, afast change from the recirculation mode to the distribution mode isobtained by instantaneously opening the distribution valve and closingthe recirculation valve. This stabilizes the throughput and the qualityof the water in the recirculation mode before changing to the volumetricdistribution mode, these functions being controlled automatically by thesystem.

A second aspect of the invention proposes a hydraulic connector thatforms a distributor or manifold for a hydraulic circuit of a fluidpurification system and has a purified fluid inlet and three outlets,the inlet being connected directly to a first outlet of the threeoutlets by a pipe and a second pipe being hydraulically connected to thefirst pipe between said inlet and said first outlet and to a third pipehaving two ends forming the other two outlets of the connector.

According to preferred features of the invention, which may whereapplicable be combined:

-   -   the hydraulic connector is a symmetrical pipework component;    -   the first pipe has an outlet section smaller than its inlet        section and the sections of the two outlets of the third pipe        are different;    -   the inlet and outlet sections of the first pipe are        substantially equal to respective outlet sections of the third        pipe;    -   the section of the second pipe is less than or equal to the        section of the first outlet of the connector.

The invention further relates to a water purification system including apurified water recirculation loop including water treatment means and atleast one point of use of purified water, the system being equipped witha connector as described above downstream of the treatment means, theinlet whereof is connected to the outlet of said treatment means and oneoutlet whereof is connected to the recirculation loop upstream of thetreatment means, the system including two parallel branches that cometogether at the point of use and are connected to the other two outletsof the connector.

The outlet of the device connected to the recirculation loop ispreferably an outlet other than said first outlet of the deviceconnected directly to the inlet by said first pipe.

According to an advantageous aspect of the invention, which may whereapplicable be combined with others, after the outlet of the treatmentmeans, downstream of the connector, the purification system is equippedwith two parallel branches that are connected to the recirculation loopat two different points downstream of the water purification means andcome together at the inlet of the point of use.

According to a preferred aspect of the invention, the loopadvantageously includes a hydraulic connector forming an H-shapeddistributor (or manifold) in the recirculation loop for connecting saidtwo parallel diversion branches thereto and ensuring continuity of therecirculation loop via the median portion of the H-shaped distributor.

In this preferred embodiment, the two parallel branches have differentfunctions according to the respective states of the recirculation valveand the distribution valve described above.

Accordingly, in this preferred embodiment of the invention, in therecirculation mode, when the recirculation valve is open and thedistribution valve closed, because of the design of the distributor andthe resulting relative pressures at the distributor inlet and outlet,the two parallel branches behave like a secondary recirculation loop,preferably with a throughput lower than that of the main recirculationloop. The throughput of the secondary recirculation loop is a functionof the geometry of the distributor and of the associated hydrauliccircuit.

In the low throughput distribution mode, both valves are open and thetwo parallel branches behave like a single branch, and each deliverspurified water to the point of use. The proportion of water distributedrelative to the water recirculated is in part a function of the sectionof the water pipes and in particular of the geometry of the H-shapedcomponent.

In the high throughput distribution mode, the two parallel branchesbehave like a single branch and deliver purified water to the point ofuse.

Providing two parallel branches does not change in any way the overalloperation of the system of the invention with two valves in the modesdescribed above.

Note that this preferred embodiment of the invention is not limited tothe use of an H-shaped hydraulic connector, and to the contrary coversall variants that will be evident to the person skilled in the art thatexploit the design with two parallel branches whereof the principles andadvantages are described above.

Moreover, it will be appreciated that the architecture with two parallelbranches enables the use of branches each having a diameter smaller thana single branch providing the same throughput as the two branchescombined.

Polyethylene (PE), polypropylene (PP) and polytetrafluoroethylene (PTFE)are particularly suitable materials for fabricating pipes forcirculating purified water in this type of system. These materials arerelatively rigid, however, especially when they take the form of a tubehaving a large diameter for distributing purified water at a highthroughput. In some applications it is beneficial to provide a flexibleconnection for distributing purified water at the point of use. In thispreferred embodiment, the structure with two parallel branches of asystem of the invention is exploited by using two parallel branches thatare preferably fabricated from PE or PP tubes and are preferably ofsufficiently small diameter to impart the required flexibility to themat the same time as being of sufficiently large diameter to allow thedistribution of purified water at the maximum throughput via the twobranches simultaneously.

Features and advantages of the invention will emerge from the followingdescription of one embodiment of a system of the invention given by wayof illustrative and nonlimiting example and with reference to theappended drawings, in which:

FIG. 1 is a diagram of a preferred embodiment of a system of theinvention in a recirculation mode;

FIG. 2 is a diagram of a preferred embodiment of a system of theinvention in a high throughput operating mode;

FIG. 3 a is a diagram of a preferred embodiment of a system of theinvention in a low throughput operating mode;

FIG. 3 b shows a variant of the FIG. 3 a preferred embodiment;

FIG. 4 is a diagram of a variant of the system shown in the precedingfigures, indicating the water treatment means; and

FIG. 5 is a diagram of a hydraulic connector 140 according to theinvention forming a distributor or manifold.

As seen in FIGS. 1 to 3 in particular, a water purification system 100of the invention includes a water supply point 101 for supplying thesystem with water to be purified via a solenoid valve 110 and arecirculation loop 106, a first portion whereof includes a pump 103, aflow meter 104 and treatment means 150 and a second portion whereofincludes a distributor or manifold 140 connected at two separate pointsto said recirculation loop 106, the first connection point being thepurified water inlet and the second point being a water outlet connectedvia the recirculation loop to a recirculation solenoid valve 130, theoutlet whereof is connected to the first portion of the system. Thedistributor 140 further includes two other connection ends respectivelyconnected to two parallel water pipes that come together at their endsopposite the distributor 140 at the inlet of a distribution solenoidvalve 120 for distributing purified water to the point of use 102,generally via a filter 107 or a finishing cartridge.

The finishing or polishing cartridge provides a final purificationspecific to the different uses of the water produced.

For a reduction in the level of pyrogens and nucleases contained in thepurified water, an ultrafilter with a cut-off below 13000 daltons isplaced in the polishing cartridge.

For a reduction of endocrine disruptors contained in the purified water,specific types of activated carbon are placed in the polishingcartridge. For other applications necessitating a very low concentrationof boron or silica or heavy metals or organics disturbing the base-linesin liquid chromatography, specific charged materials (ion exchangeresins, charged fibers, synthetic carbons, C18 grafted materials) areplaced in the polishing cartridge.

FIG. 1 shows the solenoid valve 130 open and the solenoid valve 120closed, these positions being symbolized by the letters “O” and “C”,respectively. As a result of this configuration of the valves the systemoperates in the recirculation mode, i.e. purified water is notdistributed by the system, and so all the water leaving the treatmentmeans passes through the distributor 140 to rejoin the recirculationsolenoid valve 130. In this case, because of the H-shaped design of thedistributor 140, the two parallel branches behave as a secondaryrecirculation loop and a portion of the purified water passing throughthe distributor 140 is diverted to the parallel branches in order toensure circulation of water therein, the other portion of the purifiedwater being sent directly to the recirculation loop 106 via a bridge 141of the distributor 140.

In FIG. 2, the letters “O” and “C” alongside the solenoid valves 130 and120, respectively, indicate that the system is operating in the highthroughput distribution mode. In this case, all the water purified bythe treatment means 150 is distributed to the point of use 102 via thesolenoid valve 120, the recirculation solenoid valve 130 being closed.In a configuration of the solenoid valves 130 and 120 of this kind, theparallel branches behave like a single branch, the purified waterflowing therein in the same direction, as indicated by the arrows inFIG. 2.

FIG. 3 a shows the same system in a low throughput distribution mode.Accordingly, the recirculation and distribution valves are open, asindicated by the letter “O” in this figure. In this case, the twoparallel branches outgoing from the distributor 140 behave like a singlebranch and deliver purified water to the point of use via the solenoidvalve 120, most of the purified water being recirculated directly to thesolenoid valve 130 via the loop 106.

In an alternative embodiment, a spring-loaded check valve 121 is placedbetween the parallel branches and the distribution solenoid valve 120.An alternative configuration of this kind is shown in FIG. 3 b. Thiskind of check valve reduces the throughput at the point of use in thelow throughput mode of operation without degrading the throughput in theother modes of operation.

FIG. 4 is a diagram of a system similar to that represented in FIGS. 1to 3 in which the water treatment means are indicated. Accordingly, afirst portion of the recirculation loop 106 includes a pump 103, a flowmeter 104, a pretreatment unit 151, a UV lamp 152, preferably operatingat a wavelength of 185 nm, a finishing cartridge 153, and a resistivitycell 154 that is coupled to a total organic content (TOC) sensor 155 andthe outlet whereof is connected to the inlet 142 of the distributor 140.The outlet 144 of the distributor 140 is connected in this variant tothe inlet of another distributor 160, similar to the distributor 140,and also connected via two parallel branches to a distribution valve fordistributing water to a second distribution point having an inlet 162and three outlets 163, 164 and 165. In other embodiments, using the samearchitecture but increasing the number of distributors and therefore ofpoints of use may be envisaged. Each point of use may be equipped with apolishing cartridge specific to the different uses of the user. Theoutlet of the final distributor, here the outlet 164 of the distributor160, is connected to the recirculation loop 106 on the upstream side ofthe recirculation solenoid valve 130. Moreover, in this preferredembodiment, each distribution point has a display 148, 168 for showinginformation relating to the water distributed at each of these points.In an embodiment of this type, if two (or more) users are simultaneouslydrawing off water at each of the two (or more) points of use, the highthroughput mode takes priority and the throughput is distributed to eachof the points of use as a function of the head losses.

A valve control unit 156 having a user interface and a memory for savingdata supplied by the user controls the operation of the system in thevarious modes of operation described above, in particular in thevolumetric mode of operation.

FIG. 5 shows a distributor 140 of the invention in section. It comprisestwo symmetrical T-shaped members connected at their center by a bridge141. The ends 142, 144 to be connected to the recirculation loop 106have a larger diameter than the ends 143, 145 that cooperate with thetwo parallel branches. In a preferred embodiment, the diameter of thebridge 141 is slightly less than the diameter of the ends that cooperatewith the two parallel branches. The latter diameter is preferably 6 mmand that of the ends that cooperate with the recirculation loop ispreferably 8 mm.

In this preferred embodiment, the two parallel branches consist of PEtubes, preferably with an inside diameter of 4 mm to ensure that theyare flexible.

The system of the invention may advantageously have its inlet connectedto a tank or to a loop via a pressure regulator in order to reduce thesupply pressure from approximately 34.5 kPa to approximately 13.8 kPa.

It goes without saying that many modifications or variants of the systemshown and described above will be evident to the person skilled in theart that do not depart from the scope of the invention.

1. Water purification system (100) comprising a closed waterrecirculation loop (106) supplied at one point by a water inlet (101)with water to be purified, and having at least one outlet point of useof the purified water (102) and further comprising pumping means (103)and water purification means (150) on the loop respectively downstreamof the inlet point and upstream of the at least one outlet point (102),in the water flow direction, which system is characterized in that itincludes two independent valves: a first valve (130) on the loopupstream of the pumping means (103), and a second valve (120) upstreamof the at least one point of use outlet point (102).
 2. System accordingto claim 1, characterized in that the two valves are solenoid valves ofthe type with two normally closed (NC) flow paths.
 3. System accordingto claim 2, characterized in that it further comprises a control unitfor the valves that includes a user interface.
 4. System according toclaim 3, characterized in that the valve control unit further comprisesa memory for saving data supplied by a user.
 5. System according to anyone of claims 1 to 4, characterized in that a filter or a polishingcartridge is disposed between the or each second valve and the or eachcorresponding outlet point of use.
 6. Method of using a waterpurification system according to any one of the preceding claims,characterized in that it comprises the steps of opening the first valve,called recirculation valve, and closing the second valve, calleddistribution valve, to recirculate all the water treated by thetreatment means.
 7. Method of using a water purification systemaccording to any one of claims 1 to 5, characterized in that itcomprises the steps of opening the first valve, called recirculationvalve and opening the second valve, called distribution valve, todistribute purified water at a low throughput.
 8. Method of using awater purification system according to any one of claims 1 to 5,characterized in that it comprises the steps of closing the first valve,called recirculation valve, and opening the second valve, calleddistribution valve, to distribute purified water at a high throughput.9. Method according to claim 7 or claim 8 of using a water purificationsystem according to claim 4, characterized in that it further comprisesa step of capturing a value for the volume of purified water to bedelivered entered by the user on the user interface, a step of storingthat value in the memory of the control unit and a step of automaticallydistributing the entered volume of water, wherein a fast change from arecirculation mode to a distribution mode is obtained by instantaneouslyopening the distribution valve and closing the recirculation valve. 10.Water purification system according to any one of claims 1 to 5,characterized in that it comprises a hydraulic connector (140) thatforms a distributor or manifold for the hydraulic circuit of a fluidpurification system and has a purified fluid inlet and three outlets,the inlet of the connector is connected directly to the first outlet bya pipe and a second pipe is connected hydraulically to the first pipebetween said inlet and said first outlet and to a third pipe having twoends forming the other two outlets of the system.
 11. Water purificationsystem according to claim 10, characterized in that it comprises twoparallel branches that come together downstream of the hydraulicconnector.
 12. Water purification system according to claim 11,characterized in that the two parallel branches are made frompolyethylene, polypropylene or polytetrafluoroethylene.
 13. Waterpurification method including the steps of: purifying water using watertreatment means, and circulating the purified water in a recirculationline, characterized in that it further comprises at least one of thesteps of: opening a purified water distribution line connecting therecirculation line to a purified water distribution point and openingthe purified water recirculation line to obtain distribution at a lowthroughput, and opening the water distribution line and closing therecirculation line downstream of the water distribution line to obtaindistribution at a high throughput.
 14. Water purification methodaccording to claim 13, characterized in that it further includes,independently of the foregoing steps, the step of opening thedistribution line and closing the recirculation line to obtain thedistribution of a predetermined volume of water.